1. Field of the Invention
The present invention relates to a toner for use in a developer developing an electrostatic latent image in electrophotographies, electrostatic recording and electrostatic printing, and to a method of producing the toner and an image forming method and an apparatus using the toner.
In addition, the present invention relates more specifically to a toner for use in copiers, laser printers and plain paper facsimiles directly or indirectly using an electrophotographic developing method, and to a method of producing the toner and an image forming method and an apparatus using the toner.
2. Discussion of the Background
Due to a recent strong demand for a high-quality image, developments of an electrophotographic apparatus and a toner developer in compliance with the demand are accelerated. It is essential that the toner particles have a uniform diameter for the high-quality image. When the particle diameter distribution is sharp, individual toner particles uniformly work to remarkably improve reproducibility of a micro dot image.
However, toner particles having a small and uniform diameter has less cleanability. In particular, it is impossible to stably clean the toner particles having a small and uniform diameter with a cleaning blade. One of methods of improving the cleanability suggested is to change the toner particles from spheric particles to irregular-shaped particles. The irregular-shaped toner particles have less fluidity and the cleaning blade can easily catch the toner particles. However, toner particles being too irregular-shaped do not stably work in developing and have less micro dot reproducibility.
As mentioned above, the irregular-shaped toner particles have improved cleanability, but have deteriorated fixability. Namely, the irregular-shaped toner particles has less density in a toner layer on a transfer material before fixed and a conduction in the toner layer is deteriorated when fixed, resulting in deterioration of the low-temperature fixability. In particular, when a fixing pressure is smaller than usual, the conduction is further deteriorated.
Japanese Laid-Open Patent Publication No. 11-133665 discloses a toner including polyester having a Wadell practical sphericity of from 0.90 to 1.00. However, the toner is substantially spheric and does not solve the above-mentioned cleanability problem.
A toner polymerization method includes an emulsifying polymerization method and a dissolving suspension method, which easily produce the irregular-shaped toner particles other than a suspension polymerization method. However, it is also difficult to completely remove the styrene monomer, an emulsifier and a dispersant in the emulsifying polymerization method, which is becoming a more serious problem recently when an environmental protection is particularly emphasized. In addition, a silica included in the toner as a fluidizer does not strongly adhere to a concave portion thereof and moves thereto, which often causes problems such as photoreceptor contamination and adherence to a fixing roller due to a release of the silica when the developer is used for a long time. In the dissolving suspension method, there is an advantage of using a polyester resin capable of fixing at a low temperature, but productivity deteriorates because a high molecular weight material is controlled to increase releasability in an oilless fixation and a solvent has a high viscosity as the high molecular weight material is included in a process of dissolving or dispersing a resin or a colorant in the solvent. These problems are not solved yet. Particularly, in the dissolving suspension method, Japanese Laid-Open Patent Publication No. 9-15903 discloses a toner having a shape of both sphere and concavity and convexity to improve the cleanability, but the amorphous toner without uniformity has low chargeability and a design of a high molecular weight material is not completed yet to obtain basic durability and releasability, and therefore quality of the toner is still unsatisfactory.
Because of these reasons, a need exists for a toner producing high quality images having good reproducibility of a micro dot image.